Table 4 Associations of GSTP1 genotypes with new onset asthma, stratified by participation in team sports*

No of sports played†	GSTP1 genotype				Interaction p value§
No of sports played†	No (with asthma/without asthma)	HR (95% CI)	No (with asthma/without asthma)	HR (95% CI)	Interaction p value§
	SNP3 (Ile105Val)
	Ile/Ile		Ile/Val or Val/Val
None	21/226	1 (Ref)	36/365	0.90 (0.5 to 1.6)	0.02
1–2	37/286	1.42 (0.8 to 2.5)	33/444	0.73 (0.4 to 1.3)
>2	10/46	2.66 (1.2 to 5.9)¶	5/71	0.68 (0.2 to 1.9)
p Value‡		0.03		0.41
	SNP1 (rs6591255 A>T)
	AA		AT/TT
None	20/254	1 (Ref)	37/337	1.92 (1.1 to 3.5)¶	0.08
1–2	26/282	1.17 (0.6 to 2.1)	44/448	1.87 (1.0 to 3.4)
>2	9/48	2.49 (1.1 to 5.7)¶	6/69	1.84 (0.7 to 4.8)
p Value‡		0.07		0.81

*All models are adjusted for ethnicity, community of residence, GSTM1 and SNP1/SNP3.
†Children were categorised by the number of team sports played.
‡A test for a trend was performed using the likelihood ratio test comparing full (dummy variables for 1, 2 and 2+ sports participation) to base models stratified by Ile1905Val status.
§Interaction p value was calculated from likelihood ratio test comparing full (main effect of sports, SNP and interaction term for sport category and SNP) to the base (main effect of sports and SNP only) models.
¶p value<0.05.
GST, glutathione-S-transferase; SNP, single nucleotide polymorphism.